Microstructural evolution of Mg, Ag and Zn micro-alloyed Al-Cu-Li alloy during homogenization

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• 作者：Qing LIU^a ; Rui-hua ZHU^a ; Jin-feng LI^a ; ^{lijinfeng@csu.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Yong-lai CHEN^b ; Xu-hu ZHANG^b ; Long ZHANG^a ; Zi-qiao ZHENG^a
• 关键词：Al&ndash ; Cu&ndash ; Li alloy ; homogenization ; microstructural evolution ; Al7Cu2Fe ; AlCuMn
• 刊名：Transactions of Nonferrous Metals Society of China
• 出版年：2016
• 出版时间：March 2016
• 年：2016
• 卷：26
• 期：3
• 页码：607-619
• 全文大小：4664 K

文摘

The microstructural evolution of a Mg, Ag and Zn micro-alloyed Al–3.8Cu–1.28Li (mass fraction, %) alloy ingot during two-step homogenization was examined in detail by optical microscopy (OM), differential scanning calorimetry (DSC), electron probe micro-analysis (EPMA) and X-ray diffraction (XRD) methods. The results show that severe dendritic segregation exists in the as-cast ingot. There are many secondary phases, including T_B (Al₇Cu₄Li), θ(Al₂Cu), R(Al₅CuLi₃) and S(Al₂CuMg) phases, and a small amount of (Mg+Ag+Zn)-containing and AlCuFeMn phases. The fractions of intermetallic phases decrease sharply after 2 h of second-step homogenization. By prolonging the second-step homogenization time, the T_B, θ, R, S and (Mg+Ag+Zn)-containing phases completely dissolve into the matrix. The dendritic segregation is eliminated, and the homogenization kinetics can be described by a constitutive equation in exponential function. However, it seems that the AlCuFeMn phase is separated into Al₇Cu₂Fe and AlCuMn phases, and the size of Al₇Cu₂Fe phase exhibits nearly no change when the second-step homogenization time is longer than 2 h.